In a reactor, xenon directly generated as a result of a nuclear fission reaction and xenon generated by decay of iodine generated as a result of the nuclear fission reaction have a strong neutron absorption ability. For this reason, a phenomenon called xenon oscillation in which power distribution shape in a reactor core is periodically varied is generated. When this phenomenon is generated, the deviation in power distribution in the reactor is increased, and the maximum linear power density of nuclear fuel constituting a reactor core is increased. To avoid this deviation in power distribution in the reactor, it is necessary to suppress xenon oscillation if it is generated. As a method of suppressing xenon oscillation, Patent Document 1 discloses a method of suppressing the xenon oscillation using characteristics of an elliptic locus that are specific to xenon oscillation.
Patent Document 1: Japanese Patent No. 3202430, paragraphs 0017 to 0022, FIG. 1